how do i deduct college tuition of my non-dependent child

You cannot do that. There is not currently a deduction allowed for education expenses on your federal tax return. There is an education credit for qualifying education expenses, but it would only apply in the case you had dependents.

The person who does claim the student as a dependent (or the student himself if he is not a dependent) may count the money you paid in claiming the tuition credit, on their return. 

Although the general rule, in taxes, is that you must be the one making the payment, to get the deduction or credit, there is an exception for education.